memcg: remove mem_cgroup_uncharge

Nothing uses mem_cgroup_uncharge apart from mem_cgroup_uncharge_page, (a
trivial wrapper around it) and mem_cgroup_end_migration (which does the same
as mem_cgroup_uncharge_page).  And it often ends up having to lock just to let
its caller unlock.  Remove it (but leave the silly locking until a later
patch).

Moved mem_cgroup_cache_charge next to mem_cgroup_charge in memcontrol.h.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: David Rientjes <rientjes@google.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hirokazu Takahashi <taka@valinux.co.jp>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 70789df7dab429c2fb4056793c53a7b3580a5e65..8b1c4295848b77b6808c1f451434e02e599fffb2 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -35,7 +35,8 @@ extern void mm_free_cgroup(struct mm_struct *mm);
 extern struct page_cgroup *page_get_page_cgroup(struct page *page);
 extern int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
                                gfp_t gfp_mask);
-extern void mem_cgroup_uncharge(struct page_cgroup *pc);
+extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
+                                       gfp_t gfp_mask);
 extern void mem_cgroup_uncharge_page(struct page *page);
 extern void mem_cgroup_move_lists(struct page *page, bool active);
 extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
@@ -45,8 +46,6 @@ extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
                                        struct mem_cgroup *mem_cont,
                                        int active);
 extern void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask);
-extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
-                                       gfp_t gfp_mask);
 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
 
 #define mm_match_cgroup(mm, cgroup)    \
@@ -92,14 +91,16 @@ static inline struct page_cgroup *page_get_page_cgroup(struct page *page)
        return NULL;
 }
 
-static inline int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
-                                       gfp_t gfp_mask)
+static inline int mem_cgroup_charge(struct page *page,
+                                       struct mm_struct *mm, gfp_t gfp_mask)
 {
        return 0;
 }
 
-static inline void mem_cgroup_uncharge(struct page_cgroup *pc)
+static inline int mem_cgroup_cache_charge(struct page *page,
+                                       struct mm_struct *mm, gfp_t gfp_mask)
 {
+       return 0;
 }
 
 static inline void mem_cgroup_uncharge_page(struct page *page)
@@ -110,13 +111,6 @@ static inline void mem_cgroup_move_lists(struct page *page, bool active)
 {
 }
 
-static inline int mem_cgroup_cache_charge(struct page *page,
-                                               struct mm_struct *mm,
-                                               gfp_t gfp_mask)
-{
-       return 0;
-}
-
 static inline int mm_match_cgroup(struct mm_struct *mm, struct mem_cgroup *mem)
 {
        return 1;

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 83ba13ad31e16d69d32087bf1a02285b72e3844b..1333d25163bb9a2211a2edaec7f2f1d082566052 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -697,20 +697,22 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 
 /*
  * Uncharging is always a welcome operation, we never complain, simply
- * uncharge. This routine should be called with lock_page_cgroup held
+ * uncharge.
  */
-void mem_cgroup_uncharge(struct page_cgroup *pc)
+void mem_cgroup_uncharge_page(struct page *page)
 {
+       struct page_cgroup *pc;
        struct mem_cgroup *mem;
        struct mem_cgroup_per_zone *mz;
-       struct page *page;
        unsigned long flags;
 
        /*
         * Check if our page_cgroup is valid
         */
+       lock_page_cgroup(page);
+       pc = page_get_page_cgroup(page);
        if (!pc)
-               return;
+               goto unlock;
 
        if (atomic_dec_and_test(&pc->ref_cnt)) {
                page = pc->page;
@@ -731,12 +733,8 @@ void mem_cgroup_uncharge(struct page_cgroup *pc)
                }
                lock_page_cgroup(page);
        }
-}
 
-void mem_cgroup_uncharge_page(struct page *page)
-{
-       lock_page_cgroup(page);
-       mem_cgroup_uncharge(page_get_page_cgroup(page));
+unlock:
        unlock_page_cgroup(page);
 }
 
@@ -759,12 +757,7 @@ int mem_cgroup_prepare_migration(struct page *page)
 
 void mem_cgroup_end_migration(struct page *page)
 {
-       struct page_cgroup *pc;
-
-       lock_page_cgroup(page);
-       pc = page_get_page_cgroup(page);
-       mem_cgroup_uncharge(pc);
-       unlock_page_cgroup(page);
+       mem_cgroup_uncharge_page(page);
 }
 /*
  * We know both *page* and *newpage* are now not-on-LRU and Pg_locked.